This study of 2500 persons in 50 extended pedigrees will elucidate the mechanisms by which genetic and environmental factors interact to control blood pressure and lead to hypertension. Utah investigators will conduct a clinical screening study of 2500 subjects in 50 pedigrees of 4-5 generations, most of them ascertained with the help of the population-based computer file of Utah pedigrees (currently containing over 1,000,000 persons). Data collection will include detailed questionnaires of lifestyle and habits; height, weight, skinfold thickness; multiple blood pressure measurement before and after special stress tests; multiple 12-hour urine samples for sodium, potassium, creatinine, kallikrein and prostaglandins; and blood samples for creatinine, sodium, potassium, uric acid, cholesterol, renin, hematocrit, and fasting glucose. These detailed data collected from subjects in 50 large pedigrees will be analyzed to elucidate the etiological factors for blood pressure and hypertension including: mechanisms of genetic transmission (few major genes vs. Galtonian polygenic gene frequencies, number of alleles and loci, degree of dominance); the role of environmental factor (such as sodium and calorie intake, stress, etc.) which interact with genes or affect their penetrance; and the degree of heterogeneity between pedigrees. These data will be collected at the beginning of the study and again at the end of the study in order to document, over time, those factors which may contribute significantly to elevated blood pressure.